Slow gas uptake and low pressure hysteresis on nanoporous glasses: The influence of equilibration time and particle size

• We investigate the low pressure hysteresis found on a series of nanoporous glasses.
• We applied different adsorptives at different temperatures.
• The influence of the particle size and the equilibration time is investigated.
• We show that the low pressure hysteresis is caused by an unusual slow gas uptake.
• Potential adsorption mechanisms are proposed and discussed.

The pronounced low pressure hysteresis in the gas adsorption isotherms of nanoporous glasses is investigated by means of gas adsorption experiments at low temperatures. Compared to Vycor porous glass or controlled pore glass, often being considered as model systems for gas adsorption studies, the nanoporous glasses in the present study exhibit a highly tortuous, three-dimensional pore system with distinctly smaller mean pore widths. The origin of the low pressure hysteresis is studied by varying (i) the equilibration time, (ii) the adsorptive molecules, and (iii) the particle size of the glass samples. The relationship between the low pressure hysteresis and a very slow gas uptake is discussed. Potential adsorption mechanisms are proposed.

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